The present invention relates to motorcycle drive trains and, more particularly, to a synchronous rear belt drive system for belt driven motorcycles and a method of altering the final drive ratio of such motorcycles utilizing the present rear belt drive system.
Synchronous drive belts are used extensively in industry and in the automotive industry as timing belts for driving camshafts and auxiliary components on engines. These are endless belts upon which teeth are molded for engagement with matching cavities formed in a pulley or sprocket providing a synchronous drive system.
Conventional synchronous drive belts have teeth disposed at right angles to the mid-circumferential plane of the belt. In such belt drives each individual tooth engages a corresponding pulley cavity in a manner analogous to a rack and pinion gear. This engagement results in some impact between the belt and pulley and causes air to be suddenly expelled from the pulley cavity resulting in noise.
Various efforts have been made to increase the efficiency and to reduce noise produced by such synchronous belt/pulley combinations. For example, U.S. Pat. No. 3,033,050 illustrates a belt/pulley combination wherein the belt has teeth in a so-called herringbone design to center the belt over a V-shaped pulley in order to preclude axial movement of the belt on the pulley.
U.S. Pat. No. 5,209,705 discloses a synchronous drive belt with oblique and offset teeth having at least two adjacent rows of teeth which are at oppositely balanced oblique angles to the longitudinal direction of the belt. In addition the centerlines of the teeth in the adjacent rows are offset from each other by a distance of up to 10% to 90% of their pitch. Similarly, U.S. Pat. No. 5,421,789 discloses a synchronous drive pulley having pulley cavities, which are complimentary to a synchronous drive belt that has at least two adjacent rows of obliquely angled teeth.
However, there is no teaching or suggestion that these inventions have application in the motorcycle arts and in the manner of the present invention.